<script src="https://unpkg.com/vue"></script>
<div id="app">
    <app-content>
        <my-header></my-header>
    </app-content>
</div>
<script>

    Vue.component("my-header",{
        template: '<h3>this is my-header template </h3>',
    });
    Vue.component("app-content",{
        template: '<p>this is app-content template <slot></slot></p>'
    });
    var app = new Vue({
        el: '#app'
    });
</script>